Absorption refrigeration and air conditioning systems are in common use and there are known mixtures of absorbents (bottom product) and refrigerants (distillate) with useful properties. One commonly used absorbent/refrigerant pair of fluids is water and ammonia (in some cases with a tertiary gas, for example hydrogen), the ammonia being separated from the water by a distillation process within a heated column, the ammonia gas then being condensed, passed through an expansion valve, evaporated to provide a cooling effect and then re-absorbed into the separated water stream passed out from the bottom of the distillation column.
Heretofore it has been customary to select refrigerants and absorbent fluids having quite separate and different desirable properties.
The operating conditions of temperature and pressure in the distillation column are dictated both by the nature of the absorbent and refrigerant fluids used in the system and by two external factors, namely first the temperature of the heat source available to supply thermal energy to the distillation column re-boiler, and second the available heat sink temperature of the cooling medium which is used to remove heat from the distillation column condenser and the absorber. For example at a pressure of 100 p.s.i. absolute ammonia distillate will boil (or condense) at about 14.degree. C., and the water bottom product exiting from the reboiler will boil at about 167.degree. C., the difference between these temperatures being more than 150.degree. C. The mixed liquids usually boil at an intermediate temperature depending on proportions.
The main object of this invention is to provide an absorption refrigeration system which can operate on "low grade" heat, and which can be used in conjunction with air conditioning.
The achievement of a distillation system operating on low grade heat enables thermal energy at a lower temperature to be used to separate the components in the distillation column while still maintaining a cooling medium temperature in the ambient range for the distillation column condenser.
One of the problems associated with all equipment such as distillation columns, absorbers, and heat exchangers where a vapour phase is involved is the effect of the vapour density on the size, and hence cost, of such equipment. A further object of the system is to achieve all the functions of refrigeration, air conditioning, and space heating with equipment of reduced physical size.
A still further problem that occurs in conventional systems such as the ammonia/water absorption system or the water/lithium bromide absorption system is that special precautions involving additional expense have to be taken to minimize corrosion within the system. A still further object of this invention is to provide a system wherein the dangers of corrosion have been substantially reduced.
Further the systems containing ammonia present hazards both from the point of view of toxicity and flammability. Yet another object of this invention is to provide a system wherein the dangers of accidental exposure of personnel to toxic and flammability hazards are substantially reduced.
In this invention there is a departure from the concept of the need for refrigerant and absorbent fluids to have quite separate and different desirable properties, and this invention makes use of fluids having properties which have heretofore appeared too similar to be useful in an absorption cycle.